The present invention relates to doors which are moved along a track, and more particularly, to an improved track member for use with such doors.
Doors which are rolled across an opening to cover and uncover the opening have been widely used for applications such as fire doors, and for garages, barns and aircraft hangars and like buildings. Generally, the doors are secured to a rolling device such as a trolley, through an intermediate device, such as a door hanger. The trolley in turn is supported for rolling movement along a surface, frequently provided by a track. While track and trolley arrangements can be provided along both the top and bottom of the door and doorway, our invention is concerned primarily with door track arrangements provided along the top of the door and doorway for suspending the door for rolling movement.
Despite the wide application of rolling doors as heretofore described, several problems are frequently encountered and have remained unresolved. A number of these problems are due to the track which is utilized to support the trolley, and hence the door. The most commonly used track is square or rectangular in cross section, for example, box-shaped, with a longitudinal opening along its bottom side to permit a door hanger or other device to extend therethrough to secure the door to a trolley positioned within the track. The horizontal surfaces within the track which support the trolley frequently collect foreign matter, particularly dirt and dust, which may cause the door to operate erratically and often require excessive force to operate the door. Removal of foreign matter by hand is usually impossible without removal of the door and trolley as the clearance between the door and the track is usually insufficient to permit the insertion of a cleaning tool into the track. A second major problem with the box-shaped track is due to the propensity of the sides of the track to bend or buckle under load, frequently resulting in the trolley binding against the sides of the track. Another problem with this track is the freedom of the trolley to skew along the horizontal supporting surfaces of the track which may cause the door hanger or other supporting member to bind against one or both sides of the track opening.
As a means of removing the problems of the accumulation of foreign matter in the track and the failure of the box-like track to cause the trolley to roll along the center line of the tracks, attempts have been made to utilize round track, i.e. track which has a rounded or elliptical cross section. However, while round track eliminates some of the problems of box-shaped track, other problems are created. For example, round track is generally unstable upon installation and is susceptible to deformation, particularly twisting of the track from its installed position under the weight of the door suspended therefrom. Round track does not provide a surface which is readily usable for mounting the track to a supporting surface, such as a beam or building header, and therefore brackets, frequently of elaborate design, must be utilized to install the track. The relative instability of the round track and the need for brackets causes the installation to be more expensive, and also to increase the difficulty of the installation.
It has recently been proposed to utilize rounded track having an upper surface which is partially planar. However, the recently proposed track still does not resolve the problems encountered with round track, particularly the problems of deformation of the track under the weight of the door and the need for brackets or other devices to install the track, particularly where it is desired to secure the track to the vertical side of a beam or building header.
It is therefore an object of the present invention to provide a door track which takes full advantage of the many features provided by the prior-common box-shaped track while overcoming the difficulties encountered in the use of such track.
These and other objects, features and advantages of the present invention will become apparent from the following description when considered in connection with the accompanying drawings.